BTM vs prat

BTM

noun

  • bottom 

prat

noun

  • A buttock, or the buttocks; a person's bottom. 

  • A cunning or mischievous trick; a prank, a joke. 

  • The female genitals. 

  • A fool. 

How often have the words BTM and prat occurred in a corpus of books? (source: Google Ngram Viewer )